The drive to polymer/plastic framed guns isn't only limited to striker fired guns. The trend in most handguns is gradually moving towards polymers. Mostly due to cost and competition in the market place. To remain competitive manufacturers need guns in the same entry level price point as competitors. So most introduce gunsthat are built to be competitive in price. Polymers help keep cost down. Striker fired pistols are also cheaper to produce because they often have fewer parts.

You could check out Sig for polymer framed pistols with more traditional hammer fired DA/SA and DAO configurations. And they run close in price point to striker fires pistols.